A separate video card containing a graphics chip and dedicated frame buffer memory are in common use in personal computers and workstations. Alternative architectures that integrate the functions of the graphics chip with the central processing unit (CPU), or with another standard computer component, are becoming more prevalent due to the economies of scale of manufacturing such integrated components and because the integrated design requires fewer components. Under a unified memory architecture, the graphics frame buffer memory is integrated into the main memory and contributes to the total memory bandwidth required to operate the computer.
Over the years the screen resolutions have increased substantially and can place a high demand on memory bandwidth in a unified memory architecture. For example, at a resolution of 1600×1200, 32-bit color depth at 75 MHz refresh frequency, nearly 0.55 GB/s of memory bandwidth is used to simply refresh the screen. (See Table 1).
TABLE 116 bit Color Depth24 bit Color Depth32 bit Color DepthResolution60 Hz75 Hz85 Hz60 Hz75 Hz85 Hz60 Hz75 Hz85 Hz640x4803544505366757088100800x600556978821031171101371561024x768901131281351691911802252551280x10241501882132252813193003754251600x12002202753113304124674395496231920x1080237297336356445504475593672
Thus, reducing the main memory bandwidth consumed by graphics processing in a unified memory architecture computer would correspondingly reduce the peak bandwidth requirements for the main memory and permit the use of less expensive memory devices in the computer.